High speed digital signals are used extensively for transmitting and receiving various types of data, for example, for defense and commercial applications. Data rates or speeds for high speed digital signals are typically measured in gigabits per second (GBPS). Often, the commercial or strategic value of transmitted information is a function of the speed at which it is delivered. Consequently, it is desirable to increase the data rate of such digital signals. As described further below, however, where the high speed digital signals are transmitted over copper or other electrically conductive cabling, the distance along which such signals may be reliably transmitted will shorten as the data rate increases.
Digital signals are electrical pulses as a function of time that rapidly change between two voltage levels that are commonly known as logic levels “0” and “1.” To have properly formed pulses as a function of time, the underlying voltage level must change between “0” and “1” rapidly, resulting in a time-dependent waveform that approximates a square wave with sharp edges. The sharp edges associated with a time-dependent pulse are commonly known as the rise and fall times (or edge rates) of the pulse. When convoluted in the time domain according to Fourier transform analysis, a square wave with sharp edges can be shown to be a sum of sinusoidal waveforms at a fundamental frequency and also higher-order odd harmonics of the fundamental frequency (e.g., the 3rd and 5th harmonic frequencies). To maintain the sharp edges of the square wave waveform, these contributions from the higher order odd harmonic frequencies must bear a specific relationship to the fundamental frequency. That is, the relative amplitude and phase of the different frequency contributions must be in a well-defined relationship in order to sum to create a square wave with a sharp edge.
As described above, high speed digital signals may be transmitted using copper cable or other electrically conductive cable connected to a pin contact. For example, FIG. 1 shows Twinax pin contact 100, which is a conventional electrical connector used to connect Twinax cabling. Twinax cabling, in turn, utilizes copper or other electrically conductive material as the medium that carries time-dependent voltage pulses from a signal source (not shown), and which pulses may be detected and resolved at a given location from the signal source as high speed digital signals. Pin contact 100 includes insulator 110 at a front end, cable socket 120 at a rear end for connecting to the cable, and outer body 130 that extends between the two ends. Pin contact 100 also includes two contact pins 160 that are positioned in two respective openings in insulator 110. Related conventional cabling and pin contacts that also use electric conductive cabling material, such as copper, include Quadrax cabling (not shown) and Quadrax pin contacts (not shown).
Conventional copper cable, or other electrically conductive cable, will exhibit a phenomenon called “frequency dependant cable loss.” As applied to time-dependent signals, such electrical loss refers to the attenuation of a time-dependent signal at a given frequency that is more pronounced at higher frequencies over a given length of cabling. This phenomenon is related to the so-called “skin effect,” where the current density of a current flowing within a conductor (such as copper) is greater near the surface of a cylindrical conductor than near the core of such a cylinder. Thus, the “skin effect” tends to restrict the ability of high frequency electrical currents to utilize the full cross section of a cylindrical cable, thereby resulting in a higher electrical resistance and, hence, higher electrical losses at higher frequencies.
Accordingly, a cable exhibiting “frequency dependant cable loss” will attenuate signals transmitted at the 3rd and 5th harmonics of a fundamental frequency at a given length, more so than the fundamental frequency itself (and the 5th harmonic more than the 3rd, etc.) and will thereby end up distorting the proper proportion of frequencies between the fundamental and higher order harmonics. As a function of the length over which it is transmitted, this nonlinear attenuation will cause the shape of the voltage pulse to become distorted and, specifically, to lose its sharp edges over that length. At a sufficiently large length of cable (and with a given initial distribution of pulses), such distortion increases to the point where a receiver is no longer able to accurately resolve the original set and distribution of pulses, and thereby decode the originally transmitted signal.
Accordingly, although a conventional Twinax cable and Twinax pin contact 100 may be able to carry voltage pulses associated with high speed digital signals, conventional Twinax cabling and Twinax pin contact 100 will tend to produce higher electrical losses at higher frequencies, and thus distort these underlying voltage pulses so that—over a sufficiently great length—any originally encoded signal is no longer able to be resolved.
Consequently, there is a need to provide an electrical connector that is capable of counterbalancing the inherent distortion that high speed digital signals exhibit over sufficiently great length of electrical conductive cabling, such as copper.